How can you that one day (one rotation of the earth) has occurred? Clocks (obviously) don't count.?

Question

How can you that one day (one rotation of the earth) has occurred? Clocks (obviously) don't count.

Scientifically.

Sorry:

How can you PROVE that one day (one rotation of the earth) has occurred? Clocks (obviously) don't count?

Answer 1

Pick a star and see when it passes the same virtual north/south line again. Don't use the Sun as the Earth moves relative to the sun a small amount each day.
Using the star technique, you'll measure approx 23 hours and 56 minutes

Answer 2

A number of ways.

You can set up a telescope at night and fix onto a particular star - then, the next night, when the star is exactly in the same position, you know a full rotation has occurred.

You can make a really good gyroscope (liquid helium comes to mind) - basically, you get something spinning really fast and you attach to a mount that can freely rotate in any direction. The object will continue to rotate in the same direction even though the earth (and mount) are rotating around it (it'll look to you as if the axis of rotation is changing, but it's not, you're the one who's rotating). once it points in the same direction again, the earth has made a full rotation.

You can make a sundial. Sure, this is almost a clock, but when the shadow of the sun is the same position, a full rotation has occurred.

Answer 3

how can we what??